1. Field of the Invention
The present invention relates to an electronic component with a diffusion barrier layer, e.g., a semiconductor transistor.
2. Description of Related Art
A semiconductor transistor is an electronic component having a metallic layer on a substrate made of a semiconductor material. In this instance, the metallic layer is an electrode of the semiconductor transistor, for example.
Platinum or palladium is used as a metal for the metallic layer, for example. In general, it is deposited either directly onto the surface of the semiconductor material or onto electric insulation layers on the semiconductor material. Gallium nitride is a common semiconductor material, for example. However, if the electronic component is used at temperatures above 350° C., the properties of the electronic component may deteriorate irreversibly. For example, this occurs when metal of the metallic layer diffuses or migrates into the electric insulation layer or into the semiconductor material. In the case of transistors, the metal diffusion or migration may cause the channel impedances to change, but also may cause the gate leakage currents to increase drastically. It has also been shown that semiconductor transistors having high gate leakage currents degrade considerably faster than electronic components having low leakage currents. This suggests that electro-migration stimulates a penetration of the platinum of the metallic layer into the semiconductor.
High-performance and high-frequency field-effect transistors, and blue, white, and green LEDs used in opto-electronics are examples of electronic components that use gallium nitride as a semiconductor material. Due to the large band gap of 3.4 eV and the thermal crystal stability of gallium nitride, components based on it are suitable, in principle, for operating temperatures up to approximately 700° C.
A chemically sensitive field-effect transistor is known from U.S. Pat. No. 4,437,969, for example. In this case, the electrodes are formed in a layer construction. The field-effect transistor is operated in liquid media at moderate temperatures. In order to prevent ions from the liquid medium from diffusing into the semiconductor substrate, an ion diffusion barrier is formed between the substrate and the metallic layer. However, this ion diffusion barrier does not prevent metal of the metallic layer from being able to diffuse into the semiconductor substrate at high temperatures.